1. Technical Field
An embodiment of the invention relates generally to the detection of electromagnetic energy, and in particular relates to a detector to detect extreme ultraviolet radiation.
2. Description of the Related Art
Photo-lithography processes are used to create the very small features that make up integrated circuits, by projecting high-density patterns of electromagnetic radiation onto a wafer during manufacture. Higher density integrated circuits require smaller feature sizes. However, a limiting factor in how small the features can be produced is the wavelength of the radiation used to project the pattern. Current photo-lithography techniques may use radiation in the vacuum ultraviolet (VUV) range, with a wavelength approximately in the 100–200 nanometer (nm) range, but significant increases in feature density may require the use of extreme ultraviolet (EUV) radiation, which may have a wavelength approximately in the 10–14 nm range. However, EUV radiation is highly absorbed by most materials, so EUV-based lithography may require different techniques than are used with longer wavelengths of radiation.
Controlling the amount of energy projected during the lithography operation is important, and requires determining the amount of energy in the EUV beam. Diode based sensors may be used to measure EUV intensity. Unfortunately, directing a controlled portion of the beam to a diode sensor with a beam splitter, which works well with longer wavelengths of radiation, is impractical with the high-energy EUV radiation. Conventional forms of detecting the electromagnetic energy off-axis in the lithography tool have proven to produce significant errors, since the actual dose within the path must be inferred, and controlling the percentage of energy off-axis is difficult.